This video discusses Third Trimester Bleeding:
Topic Covered:

-Vasa Previa
-Placenta Previa
-Abrupto Placenta
-Uterine Rupture

This clip will help you distinguish the difference between 3rd Trimester Bleeding causes in a way where you will never get these questions wrong again.

YouTube - USMLE ALGORITHMS: OBGYN-3rd trimester bleeding